This invention relates to security systems, and, in the preferred embodiment, to magnetically encoded data card security systems in which access at a secured location is controlled by a comparison of data on a card inserted by personnel into the system with data stored in the system and defining those persons who shall be granted access. More particularly, this invention relates to a system in which, in addition to card data, keyboard data may be entered by persons wishing access, the keyboard data being in combination and permutation of the card data. In such a system, the present invention provides a substantially broader degree of flexibility in system control than was previously available, since it permits independent programming of terminals at each of plural remote locations in a system where the remote terminals, under normal circumstances, operate in conjunction with a central processor to regulate access. Thus, with this system flexibility, it is possible, even when communication is interrupted between the central processor and the remote terminals, to limit access at the remote terminals in accordance with either (a) the same identification list as is stored in the main memory, (b) a more stringent list, or (c) a more liberal list, as the user desires. Such flexibility has not heretofore been available. Furthermore, the ability to program a memory list to define who shall be provided access at each of the independent terminals, is accomplished in the present invention in a manner which permits identification numbers to be added and deleted from the system without affecting the system's memory capacity.
Security systems utilizing remote terminals to limit access at individual remote locations have, in the past, utilized static magnetic card readers at these remote locations for controlling access through electrically operable devices, such as doors, turnstiles, printers, etc. Prior art systems have been devised in which the remote card readers communicate with a central data processor or operate as stand-alone units.
The card or badge bearing encoded data used for controlling access is typically inserted into a slot of a reader which reads and decodes the data on the card. Advantageously, this data is encoded as a plurality of magnetically polarized spots in a sheet of magnetic material. Such encoded data normally includes an identification number or numbers identifying the card holder. During use, this number encoded by the card is compared with a number or numbers stored in the central computer terminal in multiterminal systems using central processors or at the remote locations in totally stand-alone systems, all to ascertain whether the individual inserting the card is entitled to access to a building, room, parking lot, or the like.
In one prior art embodiment, the magnetically polarized spots are used to directly actuate a reed relay or other moving switch mechanism located within the reader. In the state-of-the-art system, as is exemplified by U.S. Pat. No. 3,686,479 entitled "Static Reader System For Magnetic Cards", assigned to A-T-O, Inc., assignee of the present invention, electromagnetic solid state sensors are used. These sensors are disclosed and claimed in U.S. Pat. No. 3,717,749, also assigned to A-T-O, Inc. These patents are hereby incorporated in this disclosure by reference. Such systems have been found to be very reliable and are in use as access control systems in a number of different industries, universities, and government installations.
Operation of such systems as a part of a security network employing a central processor is disclosed and claimed in U.S. Pat. No. 4,004,134, also assigned to A-T-O, Inc., and also incorporated herein by reference. This latter system incorporates a central processor which periodically and sequentially polls each of the remote terminals in the system. The remote terminals are able to transfer data to the central processor only on receipt of a polling pulse. At the central terminal, data read at the remote location from an inserted card is compared with a master list which includes those persons who shall be given access at that remote location. Such systems, in the past, have permitted a limited degree of remote terminal operation, even is some or all of the interconnecting lines between the remote terminal and the central processor have been interrupted. The systems, however, generally require that a much simpler test be made of persons wishing entrance during such degraded mode operation, and thus the group of persons allowed access at such times is, of necessity, much larger than would normally be granted access. This is a distinct disadvantage in such systems, since it does not permit a controlled programmable access under all circumstances as is often required in secured locations.
An improved system for providing degraded operation in such a central processor-oriented system is disclosed and claimed in U.S. Pat. No. 4,097,727, entitled "Circuit For Controlling Automatic Off-Line Operation of An On-Line Card Reader," assigned to A-T-O, Inc., the assignee of the present invention, and incorporated herein by reference. Even in that improved system, there is no substantial system flexibility regarding the persons who will be granted access during degraded mode operation, and it is common in a system of that type to provide access during degraded mode operation to any person having a card coded for use within the overall security system, even if it is not coded for use at this particular remote location.
The communication lines used in a security system of this type, where a central processor is utilized for controlling the operation of plural remote terminals, provide an even greater level of security if the communication lines are monitored to assure that they are not tampered with and that their integrity is not degraded. A system for accomplishing this purpose is disclosed and claimed in U.S. patent application Ser. No. 827,994, filed Aug. 26, 1977, and entitled "System For Monitoring Integrity of Communication Lines In Security Systems Having Remote Terminals," this application being assigned to A-T-O, Inc., the assignee of the present invention and incorporated herein by reference.
It has also been known in the prior art to include at the remote location a keyboard. Typically such keyboard systems require that persons wishing access, in addition to the insertion of a magnetically encoded data card, are required to enter keyboard data, typically a sequence of digits. These digits have typically comprised a particular permutation and combination of the data encoded on the employee's card, the particular permutation and combination often being different for different remote terminals. Some prior systems have used hardwired permutation and combination circuits which did not pemit alteration after the system was installed. A more advanced keyboard system, which permits programming of the particular permutation and combination after installation, is disclosed and claimed in U.S. Pat. No. 4,142,097, entitled "Remotely Programmable Keyboard Sequence For A Security System", assigned to A-T-O, Inc., the assignee of the present invention and incorporated herein by reference.
While these systems disclosed in the prior art have provided a relatively flexible, sophisticated security network, certain persistent problems have remained unsolved. One of these problems involves the fact that systems utilizing a central processor invariably provided very broadly based access during degraded communication line operation. In addition, the prior art systems in which remote terminals are used to store lists of identification numbers for selective access have permitted changes in the access lists only at the expense of reduced memory size since, in the prior art, the elimination of an identification number from a memory storage location has typically required the destruction of that memory location.
In addition, those prior art systems which utilized real-time clocks for limiting access through a particular terminal to different personnel at different times of day, have been fairly limited in their flexibility and typically required that a person be issued a new entrance card or badge if his time of entry was to be changed. Such systems, therefore, greatly reduced the flexibility of real-time access control. In addition, such systems have not provided plural overlapping time zones so that various personnel could be provided access at different times of day which were not mutually exclusive.